Dresden 2009 – scientific programme
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O: Fachverband Oberflächenphysik
O 7: Semiconductor substrates
O 7.2: Talk
Monday, March 23, 2009, 11:30–11:45, SCH A315
Impurity induced charge density oscillations in the π-bonded chains of the Si(111)-2×1 surface — •Karolin Löser1, Martin Wenderoth1, Thomas K. A. Spaeth1, Jens K. Garleff2, and Rainer G. Ulbrich1 — 1IV. Phys. Inst., Georg-August Univ. Göttingen, Germany — 2PSN, Eindhoven University of Technology, the Netherlands
The π-bonded chain in the Si(111)-2×1 reconstructed surface behaves in many respects like a quasi 1-d electronic system. Investigating such chains in P-doped Si with a low-temperature STM (6-8 K) we found extended 1-d electronic contrast induced by the substitutional Phosphorus atom. The presence of the point defect modifies the electronic properties of the chains and causes localization of electron density. The contrast feature occurs at a bias voltage of about -0.5 V and has a length of 10 nm. Depending on the lattice site of the P-atom, it is confined to either one or two neighbouring π-bonded chains.
STS data on the π-bonded chains show a Coulomb Gap in the differential tunneling conductance at EF. The Coulomb Gap has a width of up to 150 meV, depending linearly on the reciprocal length of undisturbed chain. The Coulomb Gap vanishes for undisturbed chain lengths of several hundred nm. We recently succeeded in preparing large surface areas (> 600 nm)2 without steps or domain boundaries cutting the chains. Scanning these areas we discovered that the P-atoms induce long range spatial oscillations of the LDOS along the π-bonded chains in addition to the well-known LDOS-feature. These oscillations have a wavelength of about 15 nm at a bias voltage of -0.5 V.